Prepping a new canvas

This is a huge (though it doesn't look that big in this picture) canvas, 64 x 44, that I've been preparing for a portrait of my mother.  Here I'm painting rabbit skin glue onto the raw canvas to get it ready for the next step, gesso.  The rabbit skin glue is used as an isolation, or size that separates the canvas from the gesso as they don't play well together long-term.  It also tightens the canvas down onto the strainer support.